A woman is in hospital with serious injuries after a car drove into outdoor seating at a cafe in Sydney this morning.

Two customers were sitting at an outside table at a cafe on Norton Street, Leichhardt about 9.50am when a silver BMW rolled across two lanes of traffic and drove into them.

A woman, believed to be aged in her 70s, was pinned to the wall of the cafe by the car.

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She was treated at the scene by paramedics and taken to Royal Prince Alfred Hospital in a serious but stable condition.

The other patron managed to move out of the car's path, but was thrown to the ground in the process.

CCTV vision showed bystanders sprinting towards the car in desperate attempts to stop it from hitting diners.

Witnesses rushed to the aid of the victim and helped pull her out from the crash scene.

Other bystanders ordered the driver out of the car.

He was seen rustling through items on the passenger seat before getting back into the car and fleeing the scene.

Police located the car a short time later and arrested the driver, a man believed to be aged in his 30s.

He was taken to Royal Prince Alfred Hospital under police guard for assessment.

Police are investigating the circumstances surrounding the crash.

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